1. Which kind of evidence did scientists use to determine that some animals moved back to a marine life after first evolving as land mammals? a. The fossil record
b. Comparison of homologous structures
c. DNA evidence
d. All of the above

Instead of gathering evidence from a single field, the pair pulled together research from many disciplines, including paleontology, molecular biology and conservation ecology, to give a far larger picture of what was happening when animals transitioned from the land to the sea across millennia.

Explanation:

it's probably D. all of the above because scientists use all of these examples

but im not 100% sure

i was thinking 4.0 v hope this

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.